Chapter 2- Structure And Function Of Cells Flashcards
Motor neuron
Located within the CNS that controls the contraction of a muscle or the secretion of a gland
Sensory neuron
Detects changes in the environment and send information about these changes to CNS
Interneuron
A neuron located entirely within the CNS
Central nervous system (CNS)
Brain and spinal cord
Peripheral nervous system (PNS)
Nerves
Soma
Cell body of a neuron which contains the nucleus
Dendrite
A branched, treelike structure attached to the soma of a neuron, received information from the terminal buttons of other neurons
Synapse
A junction between the terminal button of an axon and the membrane of another neuron
Axon
The long, cylindrical structure that conveys information from the soma of a neuron to its terminal buttons
Multipolar neuron
A neuron with one axon and many dendrites attached to its soma
Bipolar neuron
A neuron with one axon and one dendrite attached to its soma
Unipolar neuron
A neuron with one axon attached to its soma, the axon divides, with one branch receiving sensory information and the other sending info to CNS
Terminal button
The bud at the end of a branch of an axon, forms synapses with another neuron, sends information to that neuron
Neurotransmitter
A chemical that is released by a terminal button; has an excitatory or inhibitory effect on another neuron
Membrane
Boundary of the cell; consists of a double layer of lipid molecules
Nucleus
A structure in the central region of a cell; contains nucleolus and chromosomes
Nucleolus
A structure within the nucleus that produces ribosomes
Ribosome
A cytoplasmic structure, made of protein, that serves as the site of production of proteins translated from mRNA
Messenger ribonucleic acid (mRNA)
A macromolecule that delivers genetic information concerning the synthesis of a protein from a portion of a chromosome to a ribosome
Enzyme
A molecule that controls a chemical reaction, combining two substances or breaking a substance into two parts.
Mitochondrion
An organelle that is responsible for extracting energy from nutrients
Golgi apparatus
A complex of parallel membranes in the cytoplasm that wraps the products of the secretory cell
Exocystosis
The secretion of a substance by a cell through means of vesicles; the process by which neurotransmitters are secreted
Lysosomes
Organelles surrounded by membrane; contains enzymes that break down waste products
Microtubule
A long strand of protein filaments arranged around a hollow core; involved in transporting substances from place to place within the cell
Axoplasmic transport
An active process by which substances are propelled along mixrotubules that run the length of the axon
Anterograde
In a direction along an axon from the cell body toward terminal buttons
Retrograde
In a direction along an axon from the terminal buttons toward cell body
Glia
The supporting cells of the central nervous system (astrocytes, oligodendrocytes, microglia)
Astrocytes
Glial cell- provides nutrients and other substances and regulates the chemical composition of the extracellular fluid
Phagocytosis
The process by which cells engulf and digest other cells or debris caused by cellular degeneration
Oligodendrocyte
Glial cell that forms myelin sheaths
Myelin sheath
A sheath that surrounds axons and insulates them, preventing messages from spreading between adjacent axons
Node of ranvier
A naked portion of a myelinated axon between adjacent oligodendroglia or Schwann cells
Microglia
Smallest of glial cells; act as phagocytes and protect the brain from invading microorganisms
Schwann cell
A cell in the peripheral nervous system that is wrapped around a myelinated axon
Blood-brain barrier
A semipermeable barrier between the blood and the brain produced by the cells in the walls of the brains capillaries
Electrode
A conductive medium that can be used to apply stimulation or to record electrical potentials
Membrane potential
The electrical charge across a cell membrane; the difference in electrical potential inside and outside the cell
Resting potential
The membrane potential of a neuron when it is not being altered by excitatory or inhibitory postsynaptic potentials (-70 mV in giant squid axon)
Depolarization
Reduction (toward zero) of the membrane potential of a cell from its normal resting potential
Hyperpolarization
An increase in the membrane potential of a cell, relative to the normal resting potential
Action potential
The brief electrical impulse that provides the basis for conduction of information along an axon
Threshold of excitation
The value of the membrane potential that must be reached to produce action potential
Diffusion
Movement of molecules from regions of high concentration to regions of low concentration
Electrolyte
An aqueous solution of a material that ionizes-namely, A soluble acid, base, or salt
Ion
A charged molecule. Cations are positively charged. Anions are negatively charged
Electro static pressure
The attractive force between atomic particles charged with opposite signs or the repulsive force between atomic particles charged with the same sign
Sodium-potassium transporter
A protein found in the membrane of all cells that extrude sodium ions from and transports potassium ions into the cell
Ion channel
A specialized protein molecule that permits specific ions to enter or leave cells
Voltage-dependent ion channel
An ion channel that opens or closes according to the value of the membrane potential
All or none law
The principle that once an action potential is triggered in an axon, it is propagated, without decrement, to the end of the fiber
Rate law
The principle that variations in the intensity of the stimulus or other information being transmitted in an axon are represented by variations in the rate at which that acts on fires
Saltatory conduction
Conduction of action potentials by myelinated axon. The action potential appears to jump from one node of ranvier to the next
Postsynaptic potential
Alterations in the membrane potential of a postsynaptic neuron, produced by liberation of neurotransmitters at the synapse
Binding site
The location on a receptor proteins to which a ligand binds
Ligand
A chemical that binds with the binding site of a receptor
Dendritic spine
A small bud on the surface of a dendrite, with which a terminal button of another neuron form a synapse
Presynaptic membrane
The membrane of a terminal button that lives adjacent to the postsynaptic membrane and through which the neurotransmitter is released
Postsynaptic membrane
The cell membrane opposite the terminal button and a synapse; The membrane of the cell that receives the message
Synaptic cleft
The space between the presynaptic membrane in the postsynaptic membrane
Synaptic vesicles
A small, hollow, bead like structure found in the terminal buttons; contains molecules of a neurotransmitter
Postsynaptic receptor
A receptor molecule in the postsynaptic membrane of a synapse that contains a binding site for a neurotransmitter
Neurotransmitter-dependent ion channel
An ion channel that opens when a molecule of a neurotransmitter binds with the postsynaptic receptor
Ionotropic receptor
A receptor that contains a binding site for the neurotransmitter and an ion channel that opens when a molecule of the neurotransmitter attaches to the binding site
Metabotropic receptor
A receptor that contains a binding site for a neurotransmitter; activates an enzyme that begins a series of events that opens an ion channel elsewhere in the membrane of the cell when I molecule of the neurotransmitter attaches to the binding site
G protein
A protein coupled to a metabotropic receptor; conveys messages to other molecules when a ligand binds with and activate the receptor
Second Messenger
A chemical produced when a G protein activate; carries a signal that results in the opening of the ion channel or causes other events to occur in the cell
Excitatory postsynaptic potential (EPSP)
And excitatory depolarization of the postsynaptic membrane of a synapse caused by the liberation of a neurotransmitter by the terminal button
Inhibitory postsynaptic potential (IPSP)
And inhibitory hyperpolarization of the postsynaptic membrane of a synapse caused by the liberation of a neurotransmitter by the terminal button
Reuptake
The reentry of a neurotransmitter just liberated by a terminal button back and through its membrane, thus terminating the postsynaptic potential
Enzymatic deactivation
The destruction of a neurotransmitter by an enzyme after it’s release-for example, the destruction of acetylcholine by acetylcholinesterase
Acetylcholine
Neurotransmitter found in the brain, spinal cord, and part of the peripheral nervous system; responsible for muscular contraction
Acetylcholinesterase
The enzyme that destroys acetylcholine soon after it is liberated by the terminal buttons, terminating the postsynaptic potential
Neural integration
The process by which inhibitory and excitatory postsynaptic potential summate and control the rate of firing of a neuron
Auto receptor
Receptor molecule located on a neuron that response to the neurotransmitter released by that neuron
Presynaptic inhibition
The action of a presynaptic terminal button and axoaxonic synapse; reduces the amount of neurotransmitter released by the post synaptic terminal button
Presynaptic facilitation
The action of the presynaptic terminal button in an axoaxonic synapse; increases the amount of neurotransmitter release by the post synaptic terminal button
Gap junction
A special junction between cells that permits direct communication by means of electrical coupling
Neuromodulator
A naturally secreted substances act like a neurotransmitter except that it is not restricted to the synaptic cleft but diffuses through the extracellular fluid
Peptide
A chain of amino acids joined together by peptide bonds. Most neuromodulators, and some hormones consist of peptide molecules
Hormone
A chemical substance that is released by an endocrine gland that has effects on target cells in other organs
Endocrine gland
A gland that liberates it secretions into the extracellular fluid around capillaries and hence into the bloodstream
Target cell
The type of cell that is directly affected by a hormone or other chemical signal
Steroid
A chemical of low molecular weight, derived from cholesterol. Steroid hormones affect their target cells by attaching two receptors found within the nucleus